Today wireless communication systems are mainly used for human-centered communication and services. A trend is, however, to use wireless communication systems for communication and services mainly involving machines. This kind of communication and services are often referred to as Machine-to-Machine (M2M) communication.
Certain types of communication and services within M2M communication are expected to require that a wireless connection, provided by the wireless communication systems, is highly reliable. The wireless connection is required to be highly reliable both in terms of loss of the wireless connection and the possibility of establishing the wireless connection. In the following, the term “reliable” is used in this context. Therefore, for the above mentioned certain types of communication and services within M2M communication, a high reliability of the connection, or the possibility to establish connection, may be said to be required.
This kind of high reliability may also be required for Person-to-Machine (P2M), Person-to-Person (P2P) and Machine-to-Person (M2P) communication.
Services that may need this kind of high reliability include industrial process control services, services for alarm monitoring, services in smart grid applications, control and management of business and/or mission critical processes or services, services for monitoring critical infrastructure and services towards responders in the national security and public safety segment and other similar services.
Furthermore, high reliability for certain services may be beneficial where deployment of nodes, such as radio base station, radio network controller etc., is particularly costly. At the same time, it is desired to achieve sufficient capacity, e.g. in terms of number of connected devices, and/or coverage for the services.
Consider for example a device, such as smart meters for a smart grid, a metering, sensing or activation device, that is deployed in a network at a remote location at high cost. If there would be a failure in communication with such a device e.g. due to bad coverage and/or insufficient capacity, a manual restoration of the communication with the device or a replacement of the device with another device would be required to compensate for the failure. Such compensation may imply high labor costs, which would scale in an unacceptable manner when there are a great number of devices which often is the case in application of M2M communication.
It is known to provide connectivity for M2M devices in a number of different ways using e.g. wired or wireless connections. The wired connections may be copper wires, optical fibers, Ethernet cables or the like. The wireless connections may be provided by use of various Radio Access Technologies (RATs), such as Wi-Fi, Evolved Universal Terrestrial Radio Access Network for Long Term Evolution (EUTRAN/LTE), Universal Terrestrial Radio Access Network for High Speed Packet Access (UTRAN/HSPA), Global System for Mobile communication (GSM) for Enhanced Data GSM Environment (EDGE) Radio Access Network (GERAN) and the like. Moreover, evolutions of the aforementioned RATs as well as other Third Generation Partnership Project (3GPP) networks may be used to provide the wireless connection.
During planning of the radio access networks and/or telecommunication systems mentioned above, it is sometimes desired to set up the radio access network such as to provide a high reliability for M2M devices. High connectivity could then be provided in the following ways.
For example, the radio access network could be deployed as over-dimensioned in terms of transport and/or radio link resources. Over-dimensioning of transport resources may refer to use of optical fibers for communication from a base station, while a peak bit-rate from the base station is 800 Megabits per second and an optical fiber may handle tenth of Gigabits per second. Over-dimensioning of radio link resources refers to deployment of more base stations, antennas, use of more frequency bands, etc. than needed according to an estimated network load. The RAN is said to be over-dimensioned when it is deployed to be able to handle a worst case scenario while still having resources that are available for any upcoming communication.
As another example, so called node availability may be increased by introducing redundancy in a node by installing multiple power units for powering of the node. The node availability may relate to availability of e.g. transport nodes, radio nodes and server nodes, which communicate with the M2M device or control or support the network operation. Node availability decreases on failure of a node, which typically happens when power units for powering of the node breaks down.
As a further example, in some specific network segments, multiple paths could be introduced to avoid single point of failure. An optical fiber ring is able to cope with interruptions of one optical link by routing information in the opposite direction as compared to where the interrupted optical link is located.
A known exemplifying control system includes a controller and an electrical valve that is controlled by the controller. The controller sends reference values for controlling the opening and closing of the valve over a wireless connection. As an example, a reference value of zero means that the valve should be closed, a reference value of ten means that the valve should be completely open and a reference value of five means that the valve should be opened to midway and closed to midway. Hence, a service executing in the electrical valve receives reference values from the controller. In response thereto, the valve sends an actual value representing degree of openness of the valve. In case, the control system controls a flow of a fluid for cooling of e.g. a nuclear plant, it may have serious consequences if the valve is not controlled in an appropriate manner. Disadvantageously, a failure of the wireless connection may cause damage to both facilities and humans.
In order to reduce risks due to e.g. a failure of the wireless connection, the known control system may be operated in a safe manner at all times. The safe manner should not cause damages as described above, if there are large delays in the communication or even non existing communication between the controller and the electrical valve.